The ad campaign, launched Tuesday by the Washington, D.C.-based group Marijuana Policy Project, shows adults describing their reason for using marijuana instead of alcohol.

The ads finish with the line, "Why should I be punished?"

The group is supporting a Nov. 5 referendum in Portland that would legalize the recreational possession of marijuana of 2 ounces or less for adults 21 and over.

David Boyer, the Maine MPP representative, said the group wants to start a conversation on the safety of marijuana.

"Adults shouldn't be punished for using or possessing marijuana and this initiative would get rid of that punishment that we have today," Boyer said.

MPP said facts and science back up their claims that marijuana is less toxic than alcohol, doesn't cause hangovers, and doesn't make people rowdy.

Dr. Owen Pickus of the Maine Centers for Healthcare says that claim is not necessarily supported by any scientific evidence.

While he is not against the legalization of marijuana at a federal level, he does not support taking a back-door approach to something that is not yet regulated by the FDA.

"To suggest that one drug is better than another drug because it's less toxic is illogical," Pickus said.

Boyer says the MPP ads will run through the beginning of November.

The group 21 Reasons is calling the on the ads to be banned. The group wants the Metro Transit District to review its guidelines regarding alcohol and tobacco advertising and wants marijuana promotion to follow those same rules.